The field of this invention is counterweight assemblies.
In pipe welding it is very desirable to use automatic welding machines to weld a joint between two tubular members. The joint is positioned at a desired distance from the welding tool of the automatic welder, and then the tubular members are rotated about a substantially stationary axis so that each portion of the joint to be welded passes by the welding tool at the desired distance from the welding tool. If the welding machine is functioning properly and the spacing between the joint to be welded and the welding tool is maintained substantially constant throughout the rotation of the tubular members, the welding machine forms a much more uniform and reliable weld than can be achieved through manual welding.
In the past, however, it was difficult and sometimes uneconomical to use automatic welding machines when one of the tubular members involved in the welding had a segment with an angular or arcuate configuration extending from the main body of the tubular member. As the tubular member was rotated, the angular segment exerted a toque on the main body of the tubular member and caused the tubular member to lope or otherwise deviate from its intended axis of rotation. As a consequence, the spacing between the joint to be welded and the welding tool varied as the tubular member rotated, preventing the formation of an acceptable weld.
Prior attempts to offset the undesirable torques during rotation of tubular members having angular or arcuate segments were not completely satisfactory. Frequently, pieces of scrap metal were welded to the main body of the tubular member to offset the undesirable torques. There were several drawbacks to this approach. First, the amount of scrap metal welded on to the main body of the tubular member was determined on a trial and error basis. After some scrap metal was welded on to the main body of the tubular member, the tubular member was rotated to see if that amount of scrap metal was sufficient to offset the undesirable torques. If too much scrap metal had been welded on the tubular member, some of the scrap metal had to be removed with a cutting torch, chisel, or other means. If too little scrap metal had been welded on the main body of the tubular member, additional welding of the scrap metal was required. This trial and error application of scrap metal was frequently time consuming and uneconomical. In addition, all of the scrap metal was eventually removed from the main body of the tubular member. Thus, the welds attaching the scrap metal to the tubular member had to be broken. Further, for some specialized uses of the tubular members, the irregularities in the outer surface of the tubular member caused by the removal of the scrap metal had to be filled with weld material or other suitable materials. Then this filling material had to be smoothed so that the tubular member would have a uniform outer surface.
Known counterbalancing assemblies, such as those described in U.S. Pat. Nos. 1,678,286 and 1,770,601, did not provide a viable alternative to this scrap metal approach. These counterbalancing assemblies were not readily mountable on the uniform outer surface of the tubular member. Rather, they required a keyed mounting structure incorporated into the tubular member as well as the counterbalance system to secure the counterweight against rotational movement with respect to the shafts with which they were mounted. In addition, while such assemblies were purportedly adjustable, the extent of adjustment was limited in some of the devices. Further, when large counterbalancing torques were required, adjustment of such assemblies required a great deal of effort.
Because of the deficiencies with such prior attempts to offset the undesirable torques occuring during rotation of tubular members having angular or arcuate sections, welds involving such members were frequently accomplished manually. However, as noted above, the manual welds were not as consistantly uniform and reliable as those formed by automatic welding machines. As a result, commercial specifications often required that a very high percentage of these manual welds be X-rayed or otherwise inspected to determine whether the welds were fully satisfactory. If not, of course, the tubular members had to be rewelded, but even if the welds were satisfactory, considerable expenditures for equipment and labor to inspect those welds were necessary.